The American College of Radiology Imaging Network (ACRIN), a NCl-funded cooperative group, is dedicated to conducting rigorous, high quality clinical trials of medical imaging technologies as they relate to cancer. However, the rarity in the past of high quality trials in medical imaging has meant that few radiologists have gained the necessary skills to design and conduct trials or to lead multi-disciplinary teams. ACRIN recognizes that the success of any endeavor to conduct trials of medical imaging is dependent on increasing the cadre of investigators who are sufficiently trained in methodology and organization to develop and lead clinical trials. ACRIN is proposing a fellowship program that insures a succession of trained investigators who will ultimately improve the conduct of rigorous trials into the future and lay the foundations for broader applications of clinical trials in medical imaging. The ACRIN Fellowship program has the following objectives: 1) Train imaging researchers in a multidisciplinary environment to develop and conduct rigorous, multi-institutional clinical trials in medical imaging; 2) Develop competent clinical trials researchers for future leadership in ACRIN and other imaging clinical trials; and 3) Equip radiologists with the knowledge and skills necessary to be competitive for federal clinical research funding. The proposed program seeks to recruit and train, over a two-year program, three individuals per year. The program entails formal on-site education and progressively increasing responsibility working with ACRIN trial teams. The formal educational program will address principles of trial design and an overview of how federally funded clinical trials are developed, approved, executed, supervised, and reported. Involvement in clinical trials will provide an opportunity for fellows to apply what they have learned in the classroom to conducting trials. Fellows who have suitably progreessed will be given an opportunity to develop and lead an ACRIN trial as PI under the tutelege of Program mentors.